kramnamrof Posted December 16, 2018 Report Share Posted December 16, 2018 I have just started my winter project, fixing my crunching second gear in Spitfire. I've got the gearbox opened and have found what appears to be the problem. The teeth on the inner part of the 1st/2nd gear synchro hub are in a sorry state, see photos. I've had look on the usual sites for replacement but this appears to be no longer stocked. Does anyone know of a source for replacements or a cunning plan to fix the issue. Mark Link to comment Share on other sites More sharing options...
johny Posted December 16, 2018 Report Share Posted December 16, 2018 ha ha no dont worry, its good news as thats how its supposed to be! Looks like the gearbox is selected to 2nd so the hub is moved off its neutral position - you should be able to slide it with a bit of a push backwards over the 'damaged' teeth youve mentioned. Said hub can also move further backwards to engage first gear via the brass synchro ring you can see in the photos (its obviously a 4 synchro box as an earlier type wouldnt have this). Going by the limited info in the pics it looks to be in good order although youll need to inspect the mainshaft tip and layshaft but hopefully all you need is a new 2nd gear synchro ring..... Link to comment Share on other sites More sharing options...
Pete Lewis Posted December 16, 2018 Report Share Posted December 16, 2018 Crashing is normally due to the baulkring lacking 'rock over' this is due to the chamfers on the sleeve and dog teeth being chimbled Its these chamfered teeth angles that load the ring to baulk untill syncronised, by keeping sleeve and gear half a tooth out of line make sure the ring doesnt bottom out on its cone Not sure about your hub the detents in the splines are a way to help keep it in gear under load yours seem a bit one side distorted And the first rule of synchro is the clutch must be clearing fully synchro is driven from the mainshaft and has to speed up slow down the clutch disc with every sync.in the blick of an eye Pete Link to comment Share on other sites More sharing options...
Andrew Posted December 16, 2018 Report Share Posted December 16, 2018 Hi guys on a slightly related topic regarding gearboxes. Do you need to change the oil at regular intervals, I know it is nothing like the regularity of engine oil but is it ness army or is it just good practice. If so at what intervals. My gearbox does have a drain plug in the bottom of the box car Herald 13/60 regards andrew Link to comment Share on other sites More sharing options...
Clive Posted December 17, 2018 Report Share Posted December 17, 2018 Re oil, no changes are specified, however an oil change won't hurt at all. Be prepared to be shocked at the amount of swarf attached to the magnetic drain plug, but unless identifiable large bits are there it shouldn't be an issue. Refill with good quality GL4 (not GL5) oil, rated at EP80, 90 or 80/90. If the gearbox is a tad noisy, Moss make/sell a "no noise" Dynolite gear oil, rated at 85/140 so it doesn't thin as much when hot.(I have some to try in a diff, actually quite cheap when bought via ebay) To OP, good quality synchro rings are very difficult to track down. Afraid I can't offer any pointers here, but don't assume those sold by the normal traders will be much good. Some are supplied that are not even round.... Link to comment Share on other sites More sharing options...
johny Posted December 17, 2018 Report Share Posted December 17, 2018 Ive got every 24000 miles for both gearbox and diff (if fitted with a drain plug) but because this is so infrequent the biggest risk is allowing the level to become low. This rapidly accelerates wear so maintaining a correct oil level is much more important than changing it..... Link to comment Share on other sites More sharing options...
Pete Lewis Posted December 17, 2018 Report Share Posted December 17, 2018 They don't change gear oils as they dont have the same level of contamination as engines and all the combustion left overs it may have debris on the mag plug but it stays clear and clean , hence lack of drain plugs Overdrive lining wear will contaninate much more so the OD has a drain plug pete Link to comment Share on other sites More sharing options...
kramnamrof Posted December 18, 2018 Author Report Share Posted December 18, 2018 Pete, I notice in your strap line that you are using german baulk rings, would you be so kind as to divulge your source? Mark Link to comment Share on other sites More sharing options...
Pete Lewis Posted December 18, 2018 Report Share Posted December 18, 2018 these were from rimmers , about twice the price but they were round , have not looked to see if they offer them for 3 rails many were turned in a lathe in a chuck and they were lobed , awful they must be turned on a mandrill our truck ones were always german from otto fucks foundary ( not a good name gut experts at synchro materials) if thats any clues Pete Link to comment Share on other sites More sharing options...
johny Posted December 18, 2018 Report Share Posted December 18, 2018 Fraid I think Petes got the bigger type gearbox which uses different synchro rings to the small chassis ones like yours (and mine). Then theres two types that are not interchangeable depending on whether you have a single rail or 3 rail gearbox and I think its difficult to find a supply of guaranteed good quality for either. Its been discussed many times on here and elsewhere with no definite answer except to get lucky and find a NOS item somewhere..... It is possible to move the synchros around in your box so, for example, 1st which usually has had an easier life can be swopped with 2nd. Then the worn ring being in 1st shouldnt present any problem cos, as I said, the early versions didnt have any synchro there! Link to comment Share on other sites More sharing options...
Pete Lewis Posted December 18, 2018 Report Share Posted December 18, 2018 theres alot more to synchro than the baulk rings heres (probably upside down ) how it works from a Rootes manual the clean accurate chamfers n the sleeve and dog teeth on gear are elimentary Link to comment Share on other sites More sharing options...
johny Posted December 18, 2018 Report Share Posted December 18, 2018 One of the problems with finding good synchro rings is that generally they dont seem to have any identification marks so you dont know who the manufacturer is, where they were made, what the material specification etc. Then the suppliers never want to talk about it and of course, bearing in mind the work to install, test and prove their durability, any guarantee is pretty useless..... Link to comment Share on other sites More sharing options...
JumpingFrog Posted December 18, 2018 Report Share Posted December 18, 2018 The detent springs do fail. Always worth replacing these given their minimal cost. The detent is important as they allow pressure to be exerted on the synchro ring before the outer releases (see pdf at the end). Of course, there may be other issues too, as Pete explained. Do make sure the clutch is fully releasing as he suggested, a common symptom of this is a crunch when you select reverse (because it's sliding mesh). From the pictures, your gearbox shows signs of weak or broken detent springs. How easily can the outer be moved? They usually take a fair bit of force, wear gloves as you can easily cut yourself on the sharp dog teeth when it suddenly releases... Best bet is to get yourself a donor gearbox (or two) and mix and match the best parts. There are no good quality new synchros available for the small-chassis gearboxes as far as I know. It seems everyone sells the same reproduction ones (County?). Used synchro rings work perfectly fine providing they are carefully checked. There are two sizes of synchro ring, I believe a Spit Mk. IV gearbox will have the later large size. Be aware also of the input/main shaft bearings, the ones sold now are poor so don't change them unless required. For a replacement hub (which you need if it is as worn as it appears), it is little documented that the hub inners fitted to Midget 1500 gearboxes are made of a better material that don't wear as badly. However, there are at least two different versions; (big reverse teeth, small reverse teeth (what you have)). Synchro rings (all large size, p/n 150328) and so forth are interchangeable as they're the same gearbox but built in a different factory. The gears themselves are different (slightly different ratios). Easy to spot the difference (on a 3/4 hub), left is used MG (but still serviceable), right part is NOS Triumph: P.S. This pdf has some good diagrams describing the complete synchronisation process (slides 22-28) also clash (50-52): https://www.hoerbiger.com/upload/file/2013_basicsofsynchronizers.pdf P.P.S. You can still get a NOS second gear for a Spit Mk. IV gearbox: https://rimmerbros.com/Item--i-154479 Link to comment Share on other sites More sharing options...
johny Posted December 18, 2018 Report Share Posted December 18, 2018 Interesting, I can see the effect that broken detent springs would have but what might the symptoms be of wear on the teeth of a hub inner? Thanks Link to comment Share on other sites More sharing options...
Pete Lewis Posted December 18, 2018 Report Share Posted December 18, 2018 One triumph hubs there should only be polished markings on the hub , any relief to aid in gear is central on the hub width which triumph do not do. The detent balls and springs hold the sleeve central once engaged and stop any involuntary engagement, theres a press thro load of over 20 lbs to over come them easy to test on some simple scales once out the box Good tip always separate and refit sliding sleeves in a poly bag so you catch any escaping balls Pete Link to comment Share on other sites More sharing options...
kramnamrof Posted December 18, 2018 Author Report Share Posted December 18, 2018 It is quite easy to move the 1st/2nd gear outer. Certainly it is a lot easier than the 3rd/4th gear outer. I'll try and strip it down further over the next couple of days. I can see that I can tap out the main bearing with the 1st motion shaft assembly, but what is the best approach for the main shaft so I don't damage the bearing? As far as I can make out, the triumph manual requires a special tool to pull the bearing out of the box and off the shaft at the same time. While I think the Haynes manual is suggesting pushing the main shaft and bearing out the back of the box leaving the gear cluster behind. Link to comment Share on other sites More sharing options...
johny Posted December 18, 2018 Report Share Posted December 18, 2018 'any relief to aid in gear is central on the hub width which triumph do not do.' sorry Pete didnt understand this bit, is there some typos in it? With dismantling my non OD gearbox I tapped the mainshaft through the rear bearing from the back after having removed the circlip and speedo drive. Then I tapped the rear bearing out from inside the casing leaving the mainshaft, complete with gear cluster, free to be maneuvered out. Obviously the pukka Triumph tools are best but the job can be done safely with a bit of care...... Link to comment Share on other sites More sharing options...
Pete Lewis Posted December 18, 2018 Report Share Posted December 18, 2018 Quite a few manufacturers had a hub design which involved relief to the tooth profile in the middle of the teeth This allows the sleeve to pitch once the sleeve has fully engaged , the idea is to prevent jump outs. Another purpose of the the 3 balls is to make the sleeve a snap movement, ie makes the selection a more determined action Many find if you faf a change the rings let go halfway through a change and you get the resultant clashing The the ball and spring detent helps avoid that Pete Link to comment Share on other sites More sharing options...
johny Posted December 18, 2018 Report Share Posted December 18, 2018 ok so what problem could I expect to see on my 3 rail if I have worn teeth on the hub inner as the OP might have? Link to comment Share on other sites More sharing options...
JumpingFrog Posted December 18, 2018 Report Share Posted December 18, 2018 4 hours ago, johny said: what might the symptoms be of wear on the teeth of a hub inner? Purely speculating, but I think changes would feel "sticky" and maybe even reluctant to come out of gear. The photos appear to show that splines are no longer uniform/straight. I'd hypothesise the wear here is a result of the detent springs failing, allowing misalignment/movement of the outer, in turn causing increased fretting and wear when in gear. 2 hours ago, kramnamrof said: It is quite easy to move the 1st/2nd gear outer. Certainly it is a lot easier than the 3rd/4th gear outer. Yes, it sounds like they've failed, it shouldn't take a force much different to 3/4. There's a specification somewhere, but I personally don't see a reason to measure/shim them. I've never actually seen one shimmed in the 5 or so I've taken apart. Link to comment Share on other sites More sharing options...
johny Posted December 18, 2018 Report Share Posted December 18, 2018 I agree but I think the wear is produced by the force being transmitted from the gear thats been selected via the hub outer to the hub inner teeth and then onto the mainshaft. Then if the wear is excessive the outer hub could be difficult to disengage from the gear because itll tend to snag on the step (circled above) that the wear has produced in the hub inner teeth.... Link to comment Share on other sites More sharing options...
Pete Lewis Posted December 19, 2018 Report Share Posted December 19, 2018 certainly the worn ones in the pic are not as intended and i would suggest its a replacement hub thats not been sufficiently hardened as its more tooth deformation theres not much movement to cause that amount of spline wear the wear is probably on the drive side not overrun its not looking that oil stained ans doubt its original, ,,,,,, likely its a soft replacement from more poor aftermarket quality at some time in its life Pete Link to comment Share on other sites More sharing options...
Nick Jones Posted December 19, 2018 Report Share Posted December 19, 2018 The release tension or "push through" force is actually very important to synchro effect as it determines the amount of force applied between baulk ring and the cone on the gear itself, which in turn affects its ability to brake the gear to a halt and avoid crunching. Where the baulk ring is not gripping the cone properly (due to wear/bottoming out etc) but the release tension is correct, you will get a slow, obstructive change, but it should not crunch. Too low a release pressure will allow crunching regardless of baulk-ring condition. Nick Link to comment Share on other sites More sharing options...
daverclasper Posted December 19, 2018 Report Share Posted December 19, 2018 Hi. With regard to removing the output shaft from the case. Some folks have said the shaft will tap through the bearing quite easily. Mine required a lot of heavy whacks with a dead blow hammer. I was concerned about how much this may have stressed the bearing race, so replaced the bearing and on refit, tapped it along the shaft with a longish, strong tube with a diameter not bigger than the inner bearing face I seem to remember. There may be other/better way of removing?. Dave Link to comment Share on other sites More sharing options...
johny Posted December 19, 2018 Report Share Posted December 19, 2018 well the workshop manual shows the use of a special puller that locates on the snap ring slot of the bearing outer to pull it out of the case and along the shaft at the same time. Obviously this is more gentle on the bearing than hammer blows although saying that the manual also shows the input shaft being taken out, along with its bearing, using a slide hammer. Perhaps in your case some heating of the bearing might have helped.... Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now